linux-toradex.git/kernel/trace/ring_buffer.c, branch tegra-10.9.9

ring-buffer: Synchronize resizing buffer with reader lock

2009-11-04T05:04:20+00:00

We got a sudden panic when we reduced the size of the
ringbuffer.

We can reproduce the panic by the following steps:

echo 1 > events/sched/enable
cat trace_pipe > /dev/null &

while ((1))
do
echo 12000 > buffer_size_kb
echo 512 > buffer_size_kb
done

(not more than 5 seconds, panic ...)

Reported-by: KOSAKI Motohiro 
Signed-off-by: Lai Jiangshan 
LKML-Reference: <4AF01735.9060409@cn.fujitsu.com>
Signed-off-by: Steven Rostedt

tracing: Remove cpu arg from the rb_time_stamp() function

2009-10-24T09:07:51+00:00

The cpu argument is not used inside the rb_time_stamp() function.
Plus fix a typo.

Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt 
Cc: Frederic Weisbecker 
LKML-Reference: <20091023233647.118547500@goodmis.org>
Signed-off-by: Ingo Molnar

tracing: Fix comment typo and documentation example

2009-10-24T09:07:50+00:00

Trivial patch to fix a documentation example and to fix a
comment.

Signed-off-by: Jiri Olsa 
Signed-off-by: Steven Rostedt 
Cc: Frederic Weisbecker 
LKML-Reference: <20091023233646.871719877@goodmis.org>
Signed-off-by: Ingo Molnar

includecheck fix: kernel/trace, ring_buffer.c

2009-09-20T11:28:56+00:00

fix the following 'make includecheck' warning:

  kernel/trace/ring_buffer.c: trace.h is included more than once.

Signed-off-by: Jaswinder Singh Rajput 
Cc: Steven Rostedt 
Cc: Ingo Molnar 
Cc: Sam Ravnborg 
LKML-Reference: <1247068617.4382.107.camel@ht.satnam>

ring-buffer: typecast cmpxchg to fix PowerPC warning

2009-09-14T13:41:57+00:00

The cmpxchg used by PowerPC does the following:

  ({									 \
     __typeof__(*(ptr)) _o_ = (o);					 \
     __typeof__(*(ptr)) _n_ = (n);					 \
     (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_,		 \
				    (unsigned long)_n_, sizeof(*(ptr))); \
  })

This does a type check of *ptr to both o and n.

Unfortunately, the code in ring-buffer.c assigns longs to pointers
and pointers to longs and causes a warning on PowerPC:

ring_buffer.c: In function 'rb_head_page_set':
ring_buffer.c:704: warning: initialization makes pointer from integer without a cast
ring_buffer.c:704: warning: initialization makes pointer from integer without a cast
ring_buffer.c: In function 'rb_head_page_replace':
ring_buffer.c:797: warning: initialization makes integer from pointer without a cast

This patch adds the typecasts inside cmpxchg to annotate that a long is
being cast to a pointer and a pointer is being casted to a long and this
removes the PowerPC warnings.

Reported-by: Stephen Rothwell 
Signed-off-by: Steven Rostedt

ring-buffer: consolidate interface of rb_buffer_peek()

2009-09-10T03:54:02+00:00

rb_buffer_peek() operates with struct ring_buffer_per_cpu *cpu_buffer
only. Thus, instead of passing variables buffer and cpu it is better
to use cpu_buffer directly. This also reduces the risk of races since
cpu_buffer is not calculated twice.

Signed-off-by: Robert Richter 
LKML-Reference: <1249045084-3028-1-git-send-email-robert.richter@amd.com>
Signed-off-by: Steven Rostedt

ring-buffer: only enable ring_buffer_swap_cpu when needed

2009-09-04T23:42:22+00:00

Since the ability to swap the cpu buffers adds a small overhead to
the recording of a trace, we only want to add it when needed.

Only the irqsoff and preemptoff tracers use this feature, and both are
not recommended for production kernels. This patch disables its use
when neither irqsoff nor preemptoff is configured.

Signed-off-by: Steven Rostedt

ring-buffer: check for swapped buffers in start of committing

2009-09-04T23:38:42+00:00

Because the irqsoff tracer can swap an internal CPU buffer, it is possible
that a swap happens between the start of the write and before the committing
bit is set (the committing bit will disable swapping).

This patch adds a check for this and will fail the write if it detects it.

Signed-off-by: Steven Rostedt

ring-buffer: disable all cpu buffers when one finds a problem

2009-09-04T15:46:25+00:00

Currently the way RB_WARN_ON works, is to disable either the current
CPU buffer or all CPU buffers, depending on whether a ring_buffer or
ring_buffer_per_cpu struct was passed into the macro.

Most users of the RB_WARN_ON pass in the CPU buffer, so only the one
CPU buffer gets disabled but the rest are still active. This may
confuse users even though a warning is sent to the console.

This patch changes the macro to disable the entire buffer even if
the CPU buffer is passed in.

Signed-off-by: Steven Rostedt

ring-buffer: do not count discarded events

2009-09-04T15:43:36+00:00

The latency tracers report the number of items in the trace buffer.
This uses the ring buffer data to calculate this. Because discarded
events are also counted, the numbers do not match the number of items
that are printed. The ring buffer also adds a "padding" item to the
end of each buffer page which also gets counted as a discarded item.

This patch decrements the counter to the page entries on a discard.
This allows us to ignore discarded entries while reading the buffer.

Decrementing the counter is still safe since it can only happen while
the committing flag is still set.

Signed-off-by: Steven Rostedt